Analysis of autophagy activated during changes in carbon source availability in yeast cells
Analysis of autophagy activated during changes in carbon source availability in yeast cells
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DOI：
10.1074/jbc.ra118.005698
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发表时间：
2019-04-05
影响因子：
4.8
通讯作者：
Ohsumi, Yoshinori
中科院分区：
文献类型：
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作者：
Iwama, Ryo;Ohsumi, Yoshinori
自噬是真核生物中保守的细胞内降解系统。最近的研究表明，自噬不仅可以由氮饥饿诱导，而且还可以由许多其他刺激诱导。然而，关于诱导自噬的条件类型以及在这些特定条件下诱导的特定类型的自噬的问题仍然存在。在实验研究中，突然的营养变化经常被用来诱导自噬。在这项研究中，我们研究了在低葡萄糖培养基上分批培养的自噬诱导，其中酵母（酿酒酵母）细胞的生长清楚地反映了完全由碳源状态。在这种培养基中，细胞依次通过三个阶段：葡萄糖利用期、乙醇利用期和乙醇耗尽期。使用免疫印迹法，荧光显微镜，透射电子显微镜超微结构分析的GFP切割测定，我们发现，散装自噬和内质网吞噬诱导开始在乙醇利用阶段，散装自噬被激活到更大程度上在乙醇耗尽阶段。此外，我们发现线粒体自噬是由乙醇消耗诱导的。微自噬发生在葡萄糖耗尽后，并涉及将胞质组分和脂滴并入液泡腔。此外，我们观察到自噬缺陷细胞在乙醇利用阶段生长更慢，并且当它们从乙醇耗尽阶段转移到新鲜培养基时，生长恢复延迟。我们的研究结果表明，不同类型的自噬诱导酵母细胞经历逐渐变化的碳源供应。
Autophagy is a conserved intracellular degradation system in eukaryotes. Recent studies have revealed that autophagy can be induced not only by nitrogen starvation but also by many other stimuli. However, questions persist regarding the types of conditions that induce autophagy, as well as the particular kinds of autophagy that are induced under these specific conditions. In experimental studies, abrupt nutrient changes are often used to induce autophagy. In this study, we investigated autophagy induction in batch culture on low-glucose medium, in which growth of yeast (Saccharomyces cerevisiae) cells is clearly reflected exclusively by carbon source state. In this medium, cells pass sequentially through three stages: glucose-utilizing, ethanol-utilizing, and ethanol-depleted phases. Using GFP cleavage assay by immunoblotting methods, fluorescence microscopy, and transmission electron microscopy ultrastructural analysis, we found that bulk autophagy and endoplasmic reticulum-phagy are induced starting at the ethanol-utilizing phase, and bulk autophagy is activated to a greater extent in the ethanol-depleted phase. Furthermore, we found that mitophagy is induced by ethanol depletion. Microautophagy occurred after glucose depletion and involved incorporation of cytosolic components and lipid droplets into the vacuolar lumen. Moreover, we observed that autophagy-deficient cells grow more slowly in the ethanol-utilizing phase and exhibit a delay in growth resumption when they are shifted to fresh medium from the ethanol-depleted phase. Our findings suggest that distinct types of autophagy are induced in yeast cells undergoing gradual changes in carbon source availability.